Conventionally, a pneumatic tire has been known in which circumferential grooves and lateral grooves are formed in a tread section, and multiple land blocks are defined by the circumferential grooves and the lateral grooves. Multiple sipes (microgrooves) are formed in each of the land blocks to improve tire performance on ice (refer to Patent Document 1, for example). The sipes described in Patent Document 1 each extend from a tread surface of the land block inward in the radial direction, and are provided with an expanded diameter section at a depth ranging from 20% to 90% of the depth of the sipe.